The present invention relates to a booster and charger unit for a hand-held portable (HHP) telephone capable of preventing a casing of the booster and charger unit from being heated to excessively high temperatures.
Generally, an HHP telephone is designed with primary importance placed on the convenience of transport and, therefore, miniature, light weight, and small in transmission power. While such a telephone is of course powered by a battery, the battery is usually implemented with an economical and light weight nickel-cadmium battery which is repeatedly usable. On the other hand, the HHP telephone can be used in a car which mounts a car adapter and a booster and charger unit. The car adapter accommodates the HHP telephone and connects the telephone and the unit. The booster and charger unit includes a transmission power booster which serves to boost the transmission power and, thereby, extends the range of communication. The unit also includes a charging circuit adapted to charge a nickel-cadmium battery which has to be charged frequently due to the increase in power consumption which in turn results from the increase in output power as stated above. The transmission power booster generates a substantial amount of heat while in operation, the heat generation reaching a critical degree as a communication is continued over a long period of time. While several hours have heretofore been consumed in charging a chargeable battery, a current trend in the art is toward the use of a rapid charging system which completes charging in one hour or so. A charging circuit with the rapid charging principle, too, generates considerable heat because a large current flows through the circuit within a short period of time. A circuit of the kind generating substantial heat as stated would be damaged due to excessive temperature elevation if not provided with a sufficient countermeasure against heat radiation.
In the case of a booster and charger unit, its casing serves the function of a radiator, and circuits which generate substantial heat as described above are installed in the casing. A prerequisite is, therefore, that the casing of a booster and charger unit be dimensioned large enough to cope with a particular amount of heat generation. However, the booster and charger unit is so designed as to achieve a miniature and light weight configuration as desired to promote the ease of handling and the cut-down of cost, priority being often given to such a configuration over the area available for heat radiation. Today, therefore, the short heat radiation area available with the casing, i.e., the excessive temperature elevation of the casing is the fatal problem with a booster and charger unit for a hand-held portable telephone.